Instructor: Dr. Declan McKernan
Email: declan.mckernan@universityofgalway.ie
Course: PM309 Cardiovascular Drugs
Understand variability of blood pressure with location and cardiac cycle stages.
Identify regulation mechanisms of blood pressure, including systems and hormones involved.
Dependence on two key valves:
Atrioventricular (AV) Valves
Open/close based on pressure differences between atria and ventricles.
Open when atrial pressure > ventricular pressure during relaxation.
Semilunar Valves
Open during systole when ventricular pressure exceeds arterial pressure.
Close during diastole to prevent reflux, ensuring unidirectional blood flow.
Cardiac Cycle Phases:
Systole:
Pressure rises in ventricles causing blood ejection.
Diastole:
Ventricles fill with blood as atria contract.
Stages:
Isovolumic Relaxation: All valves closed, pressure decreases.
Atrial Systole: Atria contract, blood flows into ventricles.
Ventricular Systole: Ventricles contract, pumping blood into aorta and pulmonary artery.
Major Structures:
Aorta, vena cava, pulmonary arteries and veins, hepatic and renal arteries and veins.
Blood Vessels Classification:
Elastic Arteries
Muscular Arteries
Arterioles and Capillaries
Venules and Veins
Technique: Auscultation using a sphygmomanometer.
Procedure: Inflate cuff on the brachial artery, measure
Systolic Pressure: First Korotkoff sound.
Diastolic Pressure: Last Korotkoff sound.
Normal Values:
Systolic: 120 mmHg, Diastolic: 80 mmHg, Mean arterial pressure: ~90 mmHg.
Formula: BP = Cardiac Output (CO) x Total Peripheral Resistance.
Cardiac Output Calculation: CO = Heart Rate (HR) x Stroke Volume (SV).
Peripheral Resistance:
Depends on arteriole diameter.
Increased contraction leads to increased resistance.
Role of norepinephrine and adrenergic receptors in regulating vascular smooth muscle responses.
Receptors:
Alpha-1: Causes contraction of vascular smooth muscle.
Beta-1: Increases heart rate and myocardial contractility.
Beta-2: Induces relaxation in smooth muscles.
Vagal nerves decrease heart rate via K+ channel opening.
Sympathetic system increases heart rate through norepinephrine secretion at β1 receptors.
Baroreceptors located in carotid sinus and aortic arch sense blood pressure changes.
Renin Functions:
Enzyme released during volume depletion signals Na+/water retention, leading to vasoconstriction.
Steps of RAAS:
Renin cleaves angiotensinogen to angiotensin I, which converts to angiotensin II, causing vasoconstriction and aldosterone release.
Antidiuretic Hormone (ADH): Released from posterior pituitary; increases water retention and vasoconstriction.
Endothelium-derived mediators: Include nitric oxide (NO) and prostaglandins (PGs) that affect vascular smooth muscle tone.
Blood pressure is influenced by location, heart cycles, and is regulated systemically and locally by various factors, ensuring homeostasis.